A zeroing circuit based on hall elements and a current sensor

Abstract

A kind of zeroing circuit and current sensor based on Hall element, the present application belongs to electromagnetic induction technical field, by Hall element, detect external current induction magnetic field, and generate Hall voltage signal;Feedback coil, be located at the first end of C-shaped magnetic ring;Magnetic balance coil, be located at the second end of C-shaped magnetic ring, wherein, magnetic balance coil is oppositely arranged with feedback coil;Conditioning circuit, compare and amplify processing generation first current signal with Hall voltage signal;Wherein, first current signal flows through feedback coil, to form first electromagnetic field;Electromagnetic balance circuit, according to the voltage signal provided by conditioning circuit, adjust the current flowing in magnetic balance coil, to make the magnetic motive force generated by feedback coil equal to the magnetic motive force generated by magnetic balance coil;Wherein, the direction of the induced magnetic field generated by feedback coil and the direction of the induced magnetic field generated by magnetic balance coil are opposite;Improve the linearity of current, realize isolated sensing and high-precision sensing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electromagnetic induction, and particularly relates to a zero adjustment circuit based on a Hall element and a current sensor. BACKGROUND

[0002] At present, a traditional Hall sensor generally winds a magnetic ring through a single winding, and a magnetic field generated by a wire is contactively sensed on the magnetic ring. Due to the influence of contact materials and contact areas, a serious unbalanced voltage appears in the circuit. Even if non-contact measurement is realized by increasing a traditional current transformer, due to the influence of circuit operating temperature and varying magnetic field strength, the effect of zero adjustment is still not ideal, and the linearity and accuracy need to be improved. SUMMARY

[0003] Embodiments of the present application provide a zero adjustment circuit based on a Hall element and a current sensor, aiming to solve the problems of complex circuit and poor stability of a traditional constant current constant voltage output circuit.

[0004] A first aspect of the embodiments of the present application provides a zero adjustment circuit based on a Hall element, comprising: a Hall element, which is arranged at an opening of a C-shaped magnetic ring and is configured to detect an external current-induced magnetic field and generate a Hall voltage signal; a feedback coil, which is arranged at a first end of the C-shaped magnetic ring; a magnetic balance coil, which is arranged at a second end of the C-shaped magnetic ring, wherein the magnetic balance coil is arranged opposite to the feedback coil; a conditioning circuit, which is connected with the Hall element and the feedback coil and is configured to generate a first current signal by comparing and amplifying the Hall voltage signal; wherein the first current signal flows through the feedback coil to form a first electromagnetic field; and an electromagnetic balance circuit, which is connected with the conditioning circuit and the magnetic balance coil and is configured to adjust a current flowing through the magnetic balance coil according to a voltage signal provided by the conditioning circuit, so that a magnetic motive force generated by the feedback coil is equal to a magnetic motive force generated by the magnetic balance coil; wherein the direction of the induced magnetic field generated by the feedback coil is opposite to the direction of the induced magnetic field generated by the magnetic balance coil.

[0005] In one of the embodiments, the zero adjustment circuit based on the Hall element further comprises an electromagnetic generation circuit, which is connected with the conditioning circuit and the electromagnetic balance circuit and is configured to generate an electromagnetic field around the magnetic ring by connecting a power supply to the circular rod conductor, and the electromagnetic field is the first electromagnetic field.

[0006] In one of the embodiments, the Hall element has a cubic symmetric structure and is symmetrically arranged at equidistant centers of the opening of the C-shaped magnetic ring, forming a non-contact electromagnetic induction structure above and below the C-shaped magnetic ring.

[0007] In one of the embodiments, the conditioning circuit comprises: a comparison amplifier, a power supply, a first winding, and a first resistor; a positive input terminal of the comparison amplifier is connected with the Hall element to access the voltage signal, and serves as an input terminal of the voltage signal of the conditioning circuit; a negative input terminal of the comparison amplifier serves as a reference voltage signal input terminal of the conditioning circuit to access the reference voltage, and is configured to compare the voltage signal with the reference voltage and output a first current signal according to a comparison result; the power supply is connected with the comparison amplifier to access the first current signal, and is configured to stabilize the first current signal and supply power for the electromagnetic balance circuit; a first end of the first winding is connected with the power supply, and is configured to conduct the first current signal; a first end of the first resistor is connected with a second end of the first winding; and a second end of the first resistor is connected with a power supply ground.

[0008] In one of the embodiments, the electromagnetic balance circuit comprises: an adjustable resistor, a temperature-sensitive resistor, and a second winding; a first end of the adjustable resistor is connected with a positive electrode of the power supply of the conditioning circuit to access the positive voltage, and is configured to manually slide to adjust the resistance value according to the change of the actual current value; a first end of the temperature-sensitive resistor is connected with a second end of the adjustable resistor, and is configured to automatically adapt to the corresponding resistance value according to the temperature value of the circuit; a first end of the second winding is connected with a second end of the temperature-sensitive resistor, and is configured to conduct a second current signal; and a second end of the second winding serves as an input terminal of the negative voltage of the electromagnetic balance current, and is connected with a negative electrode of the power supply of the conditioning circuit to access the negative voltage.

[0009] In one of the embodiments, the electromagnetic generation circuit comprises: a round rod conductor fixed at a ring core position of the magnetic concentrating ring, and configured to conduct an external current and generate an electromagnetic field on the magnetic concentrating ring; and the magnetic concentrating ring is connected with the first winding and the second winding, and is configured to change the magnetic field of the first winding and the second winding according to the electromagnetic signal of the electromagnetic field generated by the round rod conductor.

[0010] In one of the embodiments, the number of turns of the feedback coil is 10 times the number of turns of the magnetic balance coil.

[0011] In one of the embodiments, the power supply comprises: a first field effect transistor and a second field effect transistor; a gate of the first field effect transistor and a gate of the second field effect transistor are connected, and serve as an input terminal of the power supply to access the first current signal; a drain of the first field effect transistor accesses the positive voltage; a source of the second field effect transistor accesses the negative voltage; a source of the first field effect transistor and a drain of the second field effect transistor are connected, and serve as an output terminal of the first current signal, and are configured to stably and continuously track the first current signal.

[0012] The second aspect of the embodiment of the application provides a current sensor comprising the above-mentioned zero adjustment circuit based on the Hall element.

[0013] Compared with the prior art, the embodiment of the application has the following beneficial effects:

[0014] The Hall element samples the electromagnetic signal of the electromagnetic field through a semiconductor Hall sensor to output a voltage signal; the conditioning circuit compares and amplifies the voltage signal into a first current signal through a comparison amplifier; the electromagnetic balance circuit forms a reverse electromagnetic field according to a preset second current signal to output an electromagnetic control signal, and the electromagnetic control signal controls the electromagnetic field of the conditioning circuit and generates a third current signal in the conditioning circuit, so that the first current signal and the third current signal are offset to each other, the linearity of the current is improved, and isolated sensing and high-precision sensing are realized. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0016] Figure 1 is a zero adjustment circuit structure schematic diagram based on a Hall element provided by an embodiment of the present application;

[0017] Figure 2 is another zero adjustment circuit structure schematic diagram based on a Hall element provided by an embodiment of the present application;

[0018] Figure 3 is a partial example circuit structure schematic diagram of a zero adjustment circuit based on a Hall element provided by an embodiment of the present application;

[0019] Figure 4 shows a partial example circuit structure schematic diagram of a zero adjustment circuit based on a Hall element provided by an embodiment of the present application;

[0020] Figure 5 shows a circuit principle structure schematic diagram of a zero adjustment circuit based on a Hall element provided by an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0022] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0023] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0024] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0025] Referring to Figure 1 , Figure 1 is a circuit structure schematic diagram of a zero adjustment circuit based on a Hall element provided by an embodiment of the present application, comprising: a Hall element 11 arranged at the opening of a C-shaped magnetic ring, configured to sample the electromagnetic signal of the electromagnetic field to output a Hall voltage signal.

[0026] It should be noted that the Hall element 11 adopts a Hall element made of a semiconductor material, and through the magnetoelectric effect, the sampling process can be realized only by inducting the electromagnetic field without contacting the related circuit during sampling the electromagnetic signal of the electromagnetic field.

[0027] The conditioning circuit 21 is connected with the Hall element 11, configured to amplify and condition the Hall voltage signal into a first current signal, and the first current signal passes through the first winding of the conditioning circuit 21 to form a first electromagnetic field.

[0028] It should be noted that when the voltage signal output by the Hall element 11 is between 0~7mV, the voltage signal is directly turned on, and the distortion or continuous voltage drift is prone to occur. Here, the conditioning circuit 21 amplifies the voltage signal and outputs a first current signal, which can avoid the above-mentioned situation, and the transmission and induction of the corresponding current signal after conditioning is more accurate.

[0029] The electromagnetic balance circuit 31 is connected with the conditioning circuit 21, and is configured to form a second electromagnetic field according to the power supply feedback of the conditioning circuit 21 to output an electromagnetic control signal, and the electromagnetic control signal controls the conditioning circuit 21, and a third current signal equivalent to and opposite to the first current signal is generated in the conditioning circuit 21.

[0030] It should be noted that when the zero adjustment circuit has a misadjustment voltage, the conditioning circuit 21 and the electromagnetic balance circuit 31 are in the same electromagnetic field and receive the same feedback of the electromagnetic signal, at this time the electromagnetic field of the electromagnetic balance circuit 31 can be ignored to affect the research, and therefore the initial magnetic field of the electromagnetic balance circuit 31 is not considered; when the conditioning circuit 21 has a misadjustment voltage, the electromagnetic balance circuit 31 is supplied with an external power supply, the potential difference of the electromagnetic balance circuit 31 changes, and the resistance values of the adjustable resistor R2 and the temperature-sensitive resistor R3 change accordingly, the second current signal generates a new magnetic field on the conditioning circuit 21, and the third current signal is generated in the conditioning circuit 21 due to the new magnetic field opposite to the initial magnetic field, so the third current and the first current are opposite.

[0031] As shown in Figure 2 A zero adjustment circuit based on a Hall element further includes an electromagnetic generation circuit 41 connected with the conditioning circuit 21 and the electromagnetic balance circuit 31, and configured to generate an electromagnetic field around the C-shaped magnetic ring according to the external power supply of the circular rod conductor, and the electromagnetic field is the first electromagnetic field.

[0032] It should be noted that the electromagnetic generation circuit 41 can generate an electromagnetic field by conducting the cylindrical conductor with an external preset current, and then the corresponding voltage is inducted by the electromagnetic detection circuit through the C-shaped magnetic ring. However, in the research, when the external preset current value is zero, due to the existence of difficult-to-handle parameters in the circuit, even if the preset current value is zero, there is still a magnetic field, which can be detected by the Hall element 11.

[0033] In one embodiment, the Hall element 11 has a cubic symmetric structure and is symmetrically arranged at the center of the C-shaped magnetic ring opening at equal intervals to form a non-contact electromagnetic induction structure above and below the C-shaped magnetic ring, and is configured to isolate the electromagnetic signal of the first electromagnetic field.

[0034] Preferably, according to the degree of linear correlation between voltage and magnetic field strength, a linear Hall sensor is selected as the core device for electromagnetic detection current, and an open-loop current sensor is specifically adopted, and a closed-loop current sensor can also be added according to the research needs.

[0035] As shown in Figure 3As shown, the conditioning circuit 21 comprises: a comparison amplifier, a power supply, a first winding N1, a first resistor R1; the positive input end of the comparison amplifier is connected with the Hall element 11 as the voltage signal input end of the conditioning circuit 21 to access the voltage signal; the negative input end of the comparison amplifier is connected as the reference voltage signal input end of the conditioning circuit 21 to access the reference voltage, configured to compare the voltage signal with the reference voltage and output a first current signal according to the comparison result; the power supply is connected with the comparison amplifier to access the first current signal, configured to stabilize the first current signal and supply power for the electromagnetic balance circuit 31; the first end of the first winding N1 is connected with the power supply, configured to conduct the first current signal; the first end of the first resistor R1 is connected with the second end of the first winding N1; the second end of the first resistor R1 is connected with the power supply ground.

[0036] It should be noted that the selection of the comparison amplifier is based on the general function of the basic comparison amplifier, and the specific selection is not limited; meanwhile, according to the research needs, a device with filtering function can be connected after the comparison amplifier to filter and process the voltage signal after comparison and amplification, so as to realize the function of stable tracking current signal, and the specific selection is not limited.

[0037] As shown in Figure 4 As shown, the electromagnetic balance circuit 31 comprises: an adjustable resistor R2, a temperature-sensitive resistor R3, and a second winding N2; the first end of the second winding N2 is connected with the second end of the adjustable resistor R2 as the positive voltage input end of the electromagnetic balance circuit 31, connected with the positive electrode of the power supply of the conditioning circuit 21 to access the positive voltage, configured to realize manual sliding adjustment of the resistance value according to the change of the actual current value; the first end of the temperature-sensitive resistor R3 is connected with the second end of the adjustable resistor R2, configured to automatically adapt to the corresponding resistance value according to the circuit temperature value; the first end of the second winding N2 is connected with the second end of the temperature-sensitive resistor R3, configured to conduct the second current signal; the second end of the second winding N2 is connected with the negative electrode of the power supply of the conditioning circuit 21 as the negative voltage input end of the electromagnetic balance circuit to access the negative voltage.

[0038] Specifically, the adjustable resistor R2 in the research selects a sliding variable resistor, which specifically comprises a terminal post, a sliding piece, a resistance wire, a metal rod and a porcelain cylinder, and is configured to set multiple preset values according to the initial magnetic field feedback signal to control the second current to be less than 10mA.

[0039] Specifically, in the research, the temperature-sensitive resistor R3 is selected as a thermistor, preferably a negative temperature coefficient thermistor (NTC thermistor), configured to decrease the coefficient with the increase of temperature; at the same time, a positive temperature coefficient thermistor (PTC thermistor) can also be selected, configured to increase the coefficient with the increase of temperature; it should be noted that the thermistors with opposite coefficients need to be tested through corresponding installation, and selected through the visibility of circuit linearity.

[0040] In one embodiment, the electromagnetic generating circuit 41 includes: a round rod conductor fixed to the ring core of the C-shaped magnetic ring, configured to conduct external current and generate an electromagnetic field on the C-shaped magnetic ring; the C-shaped magnetic ring is connected with the first winding N1 and the second winding N2, configured to change the magnetic field of the first winding N1 and the second winding N2 according to the electromagnetic signal of the electromagnetic field generated by the round rod conductor.

[0041] It should be noted that the round rod conductor can be composed of general wires or materials with good conduction function, and the specific implementation is not limited.

[0042] In one embodiment, the first winding N1 has a winding number of 10N, and N is a positive integer; the second winding N2 has a winding number of N, and N is a positive integer; the first winding N1 and the second winding N2 have consistent winding directions.

[0043] It should be noted that the first winding N1 has a feedback effect, specifically a feedback coil; the second winding N2 has a balancing effect, specifically a magnetic balancing coil; and the winding coil ratio of the two windings is N1:N2=10; preferably, the winding lines are made of φ0.05 enameled copper wire material, which has good conductivity and low loss effect.

[0044] Among them, the first winding N1 coil and the second winding N2 coil are wound on the shell of the magnetic core, and the winding directions are consistent, and the winding directions can be adjusted in real time according to the direction of the magnetic field.

[0045] In one embodiment, the power supply includes: a first field effect transistor and a second field effect transistor; the gate of the first field effect transistor and the gate of the second field effect transistor are connected, configured as the input end of the power supply connected with the first current signal; the drain of the first field effect transistor is connected with a positive voltage; the source of the second field effect transistor is connected with a negative voltage; the source of the first field effect transistor and the drain of the second field effect transistor are connected, as the output end of the first current signal, configured to stably and continuously track and amplify the first current signal.

[0046] It should be noted that the first current signal processed by the comparison amplifier can still have noise signals, at which time a filter can be connected according to the research needs to process the corresponding noise signals.

[0047] The working principle is further described below in combination with the drawings. Figures 3 to 5

[0048] The electromagnetic generating circuit 41 selects a general wire as a circular rod conductor and is fixed at the ring core position of the C-shaped magnetic ring, is connected to an external current, and generates an electromagnetic field on the C-shaped magnetic ring; the C-shaped magnetic ring is connected with the first winding N1 and the second winding N2, and the magnetic field of the first winding N1 and the second winding N2 is changed according to the electromagnetic signal of the electromagnetic field generated by the circular rod conductor.

[0049] When the preset current value outside the circular rod conductor is zero, because there are usually difficult-to-handle parameters in the circuit, even if the preset current value is zero, there is still a magnetic field, and the electromagnetic field can be detected by the Hall element 11.

[0050] Further, the Hall element 11 samples the electromagnetic signal of the electromagnetic field through the magnetoelectric effect, does not contact the related circuit, and can realize sampling by inducting the electromagnetic field to output a voltage signal to the input end of the conditioning circuit 21.

[0051] Further, the positive input end of the comparison amplifier is used as the voltage signal input end of the conditioning circuit 21 to input the voltage signal; the reverse input end of the comparison amplifier is used as the reference voltage signal input end of the conditioning circuit 21 and is connected with the reference voltage to input the reference voltage, and the voltage signal is compared with the reference voltage, and a first current signal is output according to the comparison result;

[0052] Further, the first signal passes through the power supply, and the power supply stabilizes the first current signal through the two field effect tubes in parallel, and an additional voltage is used to power the electromagnetic balance circuit 31.

[0053] Further, the first current signal flows through the first winding N1, the first resistor R1, and the power supply ground to form a complete loop, and the current value of the first current I1 of the conditioning circuit 21 is calculated according to R=I / U.

[0054] At the same time, the electromagnetic balance circuit 31 forms a complete loop according to the power supply, the adjustable resistor R2, the temperature-sensitive resistor R3, and the second winding N2, generates a second current signal I2 to form a reverse electromagnetic field, and outputs an electromagnetic control signal to control the electromagnetic field of the conditioning circuit 21, and generates a third current I3 in the conditioning circuit 21, so that the third current I3 and the first current I1 are offset to realize zero adjustment.

[0055] The second aspect of the embodiment of the application provides a zero adjustment circuit based on the Hall element.

[0056] ​The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A zeroing circuit based on a Hall element, characterized in that, include: A Hall element, wherein the Hall element is disposed at the opening of the C-shaped magnetic ring, and is configured to detect the external current-induced magnetic field and generate a Hall voltage signal; A feedback coil is located at the first end of the C-shaped magnetic ring; A magnetic balance coil is disposed at the second end of the C-shaped magnetic ring, wherein the magnetic balance coil is disposed opposite to the feedback coil; A conditioning circuit, connected to the Hall element and the feedback coil, is configured to compare, amplify, and process the Hall voltage signal to generate a first current signal; wherein the first current signal flows through the feedback coil to form a first electromagnetic field; An electromagnetic balancing circuit, connected to the conditioning circuit and the magnetic balancing coil, is configured to adjust the current flowing through the magnetic balancing coil according to the voltage signal provided by the conditioning circuit, so that the magnetomotive force generated by the feedback coil is equal to the magnetomotive force generated by the magnetic balancing coil; wherein the direction of the induced magnetic field generated by the feedback coil is opposite to the direction of the induced magnetic field generated by the magnetic balancing coil; according to the power feedback of the conditioning circuit, a second current signal is preset to form a second electromagnetic field to output an electromagnetic control signal, and the electromagnetic control signal controls the conditioning circuit, and a third current signal that is equal in magnitude and opposite in direction to the first current signal is generated in the conditioning circuit; The conditioning circuit includes: a comparator amplifier, a power supply, a first winding, and a first resistor; The positive input terminal of the comparator amplifier serves as the input terminal of the voltage signal of the conditioning circuit and is connected to the Hall element to receive the voltage signal. The inverting input terminal of the comparator amplifier serves as the reference voltage signal input terminal of the conditioning circuit, and is configured to compare the voltage signal with the reference voltage and output the first current signal based on the comparison result. The power supply is connected to the comparator amplifier to receive the first current signal, configured to stabilize the first current signal, and to supply power to the electromagnetic balance circuit. The first end of the first winding is connected to the power supply and configured to conduct the first current signal. The first end of the first resistor is connected to the second end of the first winding; The second end of the first resistor is connected to the power supply ground.

2. The Hall element-based nulling circuit of claim 1, wherein, Also includes: An electromagnetic generation circuit, connected to the conditioning circuit and the electromagnetic balance circuit, is configured to generate an electromagnetic field around the magnetic ring based on an external power supply connected to the round rod conductor, and the electromagnetic field is the first electromagnetic field.

3. The Hall element-based nulling circuit of claim 1, wherein, The Hall element has a cuboid symmetrical structure and is symmetrically arranged at the center of the opening of the C-shaped magnetic ring at equal intervals, forming an electromagnetic induction structure that is not in contact with the upper and lower parts of the C-shaped magnetic ring.

4. The Hall element-based zeroing circuit of claim 2, wherein, The electromagnetic balance circuit comprises an adjustable resistor, a temperature-sensitive resistor and a second winding, a first end of the adjustable resistor is connected with a positive electrode of a power supply of the conditioning circuit to access a positive voltage, and is configured to realize manual sliding adjustment of a resistance value according to a change in an actual current value; a first end of the temperature-sensitive resistor is connected with a second end of the adjustable resistor, and is configured to automatically adapt to a corresponding resistance value according to a circuit temperature value; a first end of the second winding is connected with a second end of the temperature-sensitive resistor, and is configured to conduct a second current signal, a second end of the second winding is connected with a negative electrode of the power supply of the conditioning circuit to access a negative voltage, and serves as an input end of a negative voltage of an electromagnetic balance current.

5. The Hall element-based zeroing circuit of claim 4, wherein, The electromagnetic generation circuit comprises: a round rod conductor fixed at a ring core position of the magnetic concentrating ring, configured to conduct an external current and generate an electromagnetic field on the magnetic concentrating ring; the magnetic concentrating ring is connected with the first winding and the second winding, and is configured to change magnetic fields of the first winding and the second winding according to an electromagnetic signal of the electromagnetic field generated by the round rod conductor.

6. The Hall element-based nulling circuit of claim 1, wherein, The number of turns of the feedback coil is 10 times the number of turns of the magnetic balance coil.

7. The Hall element-based nulling circuit of claim 1, wherein, The power supply comprises a first field effect transistor and a second field effect transistor. A gate of the first field effect transistor is connected with a gate of the second field effect transistor, and the power supply is connected with an input end of the first current signal; a drain of the first field effect transistor is connected with a positive voltage; a source of the second field effect transistor is connected with a negative voltage; a source of the first field effect transistor is connected with a drain of the second field effect transistor, serving as an output end of the first current signal, and is configured to stably and continuously track the first current signal.

8. A current sensor, characterized by The zeroing circuit based on the Hall element comprises any one of claims 1 to 7.

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